A color filter is an essential component of a solid-state imaging device or a liquid crystal display. In particular, as to a color filter for solid-state imaging device, improvement in color separation property and improvement in color reproducibility have been required.
Such a color filter is formed with colored regions (colored cured film) of plural hues and usually formed with at least red, green and blue colored regions (hereinafter, also refer to as “colored pattern” or “colored pixel”). In a method for forming a colored pattern, first, as to a first hue, a colored radiation-sensitive composition containing any of red, green and blue coloring agents is coated, followed by performing exposure, development and, if desired, heat treatment to form a colored pattern of the hue and then, as to a second hue and a third hue, the same processes of coating, exposure, development and, if desired, heat treatment are repeated.
As the coloring agent in the color filter, a pigment has been widely used because of having clear color tone and high coloring power, and in particular, it is preferred to use a pigment miniaturized and exhibiting a preferable color separation property.
Also, in a solid-state imaging device, it is required recently to miniaturize a colored pixel (for example, a colored pattern having one side of 1.0 μm or less) for the purpose of improving resolution, but it is known that noise increases with the miniaturization of the colored pixel.
The solid-state imaging device is utilized as a light sensor in various uses.
For example, a near infrared ray is hardly scattered because of having a long wavelength in comparison with visible light and it is also possible to utilize in distance measurement, three-dimensional measurement and the like. Also, since the near infrared ray is not visible to the eyes of human, animal and the like, when a subject is irradiated with a near-infrared light source at night, the subject does not notice the irradiation so that it can be used for shooting a nocturnal wild animal or for security without stimulating the subject. A light sensor sensing such a near infrared ray is capable of expansion in various uses, and development of a color filter which can be used in a solid-state imaging device sensing the near infrared ray has been awaited.
For example, a resin black matrix which has a small light absorption in a wavelength region from near infrared to infrared and has a high light transmittance in this wavelength region is known (for example, Patent Document 1), but transmission in the near infrared region is still insufficient and it is difficult to be used as an infrared transmission filter in an infrared sensor for detecting the near infrared region.
Also, an infrared transmission filter having a very thin thickness (for example, thickness of 0.5 μm) has been requested in recent years. However, as the thickness is decreased, a light-shielding property to visible light of the infrared transmission filter is apt to decrease (that is, noise derived from the visible light component is apt to generate) and as a result, a problem arises in that the performance of the infrared sensor is deteriorated.